The Cell and Tissue Analysis Core Facility (formerly Histopathology) was established in 1986 in response to the need of Center investigators for plastic glycol-methacrylate (GMA)-embedded tissue sections for histopathologic evaluations. The plastic tissue sections (1-2 um thick) enable a resolution halfway between standard paraffin-embedded sections and sections observed under low magnification in an electron microscope. In GMA sections, cells and cell components not readily seen in standard paraffin-embedded sections can be easily visualized [e.g., mast cells and basophils (and their granules), capillary endothelial cells and pericytes, and basement membranes]. Since its inception, this Core Facility has expanded the services offered to Center investigators to accommodate the growing need for expert assistance with immunocytochemical analyses of tissue samples and cultured cells as well as the preparation of publication quality photomicrographs. In the advent of the sequencing of the human genome and the rapid advances in genomics, proteomics and metabonomics, it is becoming clear that determining the physiological relevance of these global changes in DNA expression will require imaging of these molecular changes at the level of cells and tissues, using techniques such as in situ hybridization, tissue arraying, FRET, FRAP and imaging of green fluorescent protein (GFP)-labeled proteins in live cells. Thus, the investigators anticipate that the need for the Cell and Tissue Analysis Core Facility will continue to grow in the future. The Core provides: 1) a wide range of histological and cytological services; (2) photographic and digital imaging; and, (3) professional consultation to NIEHS Center members and those in their laboratories. Through the Core facility, Center investigators also have cost-effective access to equipment and services available through the Johns Hopkins University School of Medicine Microscopic Facility. The Core Facility Directors and staff also keep abreast of new developments in histopathology, cell imaging and digital photography and help Center investigators choose and develop the appropriate techniques for their research projects, analyze and interpret their data, and ultimately organize and prepare their results for publication and presentation. The overall objective of the Cell and Tissue Core Facility is to provide histopathology and cell imaging services, so that pathophysiological and toxicological investigations will be backed by morphological data at both the level of cells and tissues.